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A minimum detectable signal is a signal at the input of a system whose power allows it to be detected over the background electronic noise of the detector system. It can alternately be defined as a signal that produces a signal-to-noise ratio of a given value m at the output.
Noise-equivalent power (NEP) is a measure of the sensitivity of a photodetector or detector system. It is defined as the signal power that gives a signal-to-noise ratio of one in a one hertz output bandwidth. [1] An output bandwidth of one hertz is equivalent to half a second of integration time. [2] The units of NEP are watts per square root ...
Specific detectivity is given by =, where is the area of the photosensitive region of the detector, is the bandwidth, and NEP the noise equivalent power in units [W]. It is commonly expressed in Jones units ( c m ⋅ H z / W {\displaystyle cm\cdot {\sqrt {Hz}}/W} ) in honor of Robert Clark Jones who originally defined it.
On one side of the detector is a high-voltage cathode plane, used to establish a drift electric field across the TPC. Although the exact electric potential at which this is set is dependent on the detector geometry, this high-voltage cathode typically produces a drift field of 500 V/cm across the detector.
In that case, a fixed threshold level can be chosen that provides a specified probability of false alarm, governed by the probability density function of the noise, which is usually assumed to be Gaussian. The probability of detection is then a function of the signal-to-noise ratio of the target return. However, in most fielded systems ...
The Fano factor can be viewed as a kind of noise-to-signal ratio; it is a measure of the reliability with which the waiting time random variable can be estimated after several random events. For a Poisson counting process , the variance in the count equals the mean count, so F = 1 {\displaystyle F=1} .
The actual input signals to the phase detector, however, are not α and β, but rather sinusoids such as sin(α) and cos(β). In general, computing the phase difference would involve computing the arcsine and arccosine of each normalized input (to get an ever-increasing phase) and doing a subtraction. Such an analog calculation is difficult.
The 'drift' concept of the SDD (which was imported from particle physics) allows significantly higher count rates coupled with a very low capacitance of the detector. In older detector designs, the collection electrode is centrally located with an external FET ( field effect transistor ) to convert the current into a voltage and thus represents ...